Growth and leaf gas exchange in Populus euphratica across soil water and salinity gradients

Soil water and salinity conditions of the riparian zones along the Tarim River, northwest China, have been undergoing alterations due to water use by human or climate change, which is expected to influence the riparian forest dominated by an old poplar, Populus euphratica. To evaluate the effects of such habitat alterations, we examined photosynthetic and growth performances of P. euphratica seedlings across experimental soil water and salinity gradients. Results indicated that seedlings were limited in their physiological performance, as evidenced by decreases in their height and biomass, and the maximal quantum yield of photosystem II (PSII) photochemistry (F_v/F_m), the effective quantum-use efficiency of PSII (F_v′/F_m′), and photochemical quenching (q_P) under mild (18% soil water content, SWC; 18.3 g kg^?1 soil salt content, SSC) and moderate (13% SWC, 22.5 g kg^?1 SSC) water or salinity stress. However, seedlings had higher root/shoot ratio (R/S), increased nonphotochemical quenching (NPQ), and water-use efficiency (WUE) relative to control under such conditions. Under severe (8% SWC, 27.9 g kg^?1 SSC) water or salinity stress, P. euphratica seedlings had only a fifth of biomass of those under control conditions. It was also associated with damaged PSII and decreases in WUE, the maximal net photosynthetic rate (P _Nmax), light-saturation point (LSP), and apparent quantum yield (_α). Our results suggested that the soil conditions, where P.euphratica seedlings could grow normally, were higher than ～ 13% for SWC, and lower than ～22.5 g kg^?1 for SSC, the values, within the seedlings could acclimate to water or salinity stress by adjusting their R/S ratio, improving WUE to limit water loss, and rising NPQ to dissipate excessive excitation energy. Once SWC was lower than 8% or SCC higher than ～28 g kg^?1, the seedlings suffered from the severe stress.     

Species-specific responses to drought,salinity and their interactions in Populus euphratica and P. pruinosa seedlings

干旱和盐胁迫是严重的非生物胁迫因子,限制植物的生长和生产力,特别是在沙漠地区。本研究采用两种沙漠杨树—胡杨(Populus euphratica)和灰杨(P. pruinosa)幼苗,比较它们对干旱、盐胁迫和两者交互胁迫的耐受性。研究了在干旱、盐胁迫和交互胁迫下,胡杨和灰杨在生长、光合能力和色素含量、非结构性碳水化合物浓度、Cl⁻分配、渗透调节和活性氧积累等方面的物种特异性响应。研究结果表明, 与胡杨相比,灰杨在干旱、盐胁迫,特别是交互胁迫下表现出更高的生长抑制作用,光合作用下降,气孔关闭和活性氧积累,抗氧化酶活性和渗透调节能力下降。此外,在盐胁迫下,胡杨限制了盐从根部向叶片的转运,并且向粗根分配的Cl⁻较多,向叶片分配的Cl⁻较少,而灰杨向叶片分配较多的Cl⁻。表明这两种杨树存在着物种特异性变化,在干旱、盐胁迫,特别是交互胁迫下,灰杨受到更大的负面作用。因此,在未来干旱和盐胁迫加重的气候环境下,在生态恢复和植树造林时,应考虑这两种杨树对干旱和盐胁迫的物种特异性响应和耐受性。     

胡杨、灰叶胡杨开花生物学特性研究

从居群水平研究了胡杨、灰叶胡杨不同居群的开花物候特征.结果表明:胡杨、灰叶胡杨各居群均表现为雄株开花物候早于雌株,一般可授期开始较散粉期晚1～4 d,结束较散粉期晚2～5 d,并且居群散粉期和可授期的重叠期较长.在同一居群内,胡杨、灰叶胡杨同性单株间开花期的不一致性较高.两个种相比较,胡杨居群的开花进程比灰叶胡杨居群早2～5 d,并且从每日开花株数累积分布来看,胡杨散粉期、可授期为双峰型,灰叶胡杨为单峰型.     

Expression profiling and functional characterization of a CBL-interacting protein kinase gene from Populus euphratica

Key message

This is the first report on the function of a member of the CIPK family in Populus euphratica.

Abstract

The Ca²⁺-dependent salt overly sensitive (SOS) pathway has been shown to play an essential role in maintaining ion homeostasis and conferring salt tolerance. One component of the SOS pathway, SOS1, was identified in the salt-resistant tree P. euphratica. In this study, we identified and functionally characterized another component of the SOS pathway in this tree called PeSOS2 or PeCIPK26. On the basis of protein sequence similarity and complementation studies in Arabidopsis, PeCIPK26 was concluded to be the functional homolog of Arabidopsis AtSOS2. Yeast two-hybrid assays revealed that PeCIPK26 can interact with four calcineurin B-like (CBL) genes, i.e., PeCBL1, PeCBL4/PeSOS3, PeCBL9 and PeCBL10. Autophosphorylation assays showed that PeCIPK26 is an active protein kinase. Expression profile analysis demonstrated that PeCIPK26 is expressed in root, stem and leaf, and throughout the cell including cell membrane, cytoplasm and nucleus; in addition, it can be induced under salt-stress treatment. Functions of PeCIPK26 in salt tolerance were evaluated by gene overexpression in Arabidopsis cipk24 mutants. The better salt tolerance of transgenic plants relative to mutants was shown by their higher germination rate, lower Na⁺ accumulation and higher capacity to discharge Na⁺ when grown with NaCl. These results suggest the involvement of PeCIPK26 in the salt-stress response of P. euphratica.     

胡杨离体器官发生及试管无性系的建立

研究了离体条件下胡杨（Ｐｏｐｕｌｕｓ　ｅｕｐｈｒａｔｉｃａ　Ｏｌｉｖｅｒ）茎段、叶片及愈伤组织的器官发生和植株再生技术。离体培养以ＭＳ为基本培养基并附加４０ｍｇ／Ｌ腺嘌呤和５００ｍｇ／Ｌ水解乳蛋白。离体叶片和茎段在ＢＡ为０．５ｍｇ／Ｌ和ＮＡＡ为０．５ｍｇ／Ｌ的培养基上诱导产生愈伤组织,并在含０．２５ｍｇ／ＬＢＡ和０．５ｍｇ／ＬＮＡＡ的培养基上继代增殖。ＢＡ为０．５ｍｇ／Ｌ和ＮＡＡ为０．１ｍｇ／Ｌ可诱导叶片和愈伤组织发生不定芽,诱导频率分别为１００％和８２．９％,对于茎段,ＢＡ和ＮＡＡ分别为０．１ｍｇ／Ｌ和０．０１ｍｇ／Ｌ时诱导不定芽频率可达８３％。试管苗在大量元素减半并附加０．０１５ｍｇ／ＬＮＡＡ的ＭＳ培养基上诱导生根,生根率达８６．２％。     

Organogenesis and Plantlet Regeneration in Vitro of Populus euphratica

The research of organogenesis and in vitro plantlet regeneration of Populus euphratica Oliver was carried out using the tender shoots from mature tree as initial explants and MS medium as the basic medium. The effects of plant growth regulators (PGR) on the regeneration were compared. The results showed that the concentration of PGR was not strictly required for the organogenesis of the excised organs and callus, but the ratio of BA to NAA was important. Calli could be induced from the excised leaves and stems cultured on the medium with 0.5 mg/L BA and 0.5 mg/L NAA. The embryonic callus could be multiplied in dark on the medium supplemented with 0.25 mg/L BA and 0.5 mg/L NAA. For the adventitious bud regeneration of the leaf and callus, supplement with 0.5 mg/L BA and 0.1 mg/L NAA was appropriate, giving a regeneration frequency of 82.9% and 100%, respectively. The suitable level of BA and NAA for the excised stem's was 0.1 mg/L and 0.01 mg/L respectively, yielding a regeneration frequency of 83 %. Rooting occurred on the MS medium with half strength of macronutrient and addition of 0.015 mg/L NAA, and the rooting rate could reach up to 86.2%. The techniques of somatic cell cloning of P. euphratica was established in vitro. The problems of deterioration of the subcultured shoots were also discussed.     

胡杨种子散布的时空分布格局

以额济纳胡杨为研究对象,对种子雨的散布时间、强度、散布距离以及种子雨和空气湿度、风之间的关系进行了研究。胡杨种子雨可以分为初始期、高峰期和消退期3个阶段,大部分的种子集中在高峰期落下。种子的散布主要受湿度和风的影响。湿度对种子雨的强度起主要作用,在一天之中,种子在湿度较低的中午和下午集中散落。应用一元线性回归模型对种子雨强度和相对湿度进行分析后表明二者之间存在显著的负相关关系。对种子的散播距离进行研究后发现,大部分种子落在母树附近,少部分种子能够进行长距离传播。风对种子的传播的方向和距离起决定性的作用,不同方向上的种子传播距离和强度相差很大。在顺风方向上,种子的传播距离最远,所有的长距离传播现象几乎都发生在这一方向上;而在主风向的垂直方向和逆风方向上,种子的散布距离较小,很少有种子能够进行长距离传播。对风的观测表明中午后和下午初的风力较强,而此时种子雨强度又最大,有利风力条件和高种子雨强度出现的同步性可能是促进胡杨种子进行长距离传播最有效的生物控制机制。由于胡杨种子在自然条件下的存活时间非常短暂,所以研究中不同胡杨母树林间种子散播时间的差异可能是胡杨种群内部为适应不同洪水期所表现出的风险分摊机制所造成的。     

胡杨器官和体胚发生方式的植株再生

目的：为以胡杨为亲本的体细胞杂交育种奠定基础。方法：以胡杨苗叶片为外植体,通过器官和体胚两种不同发生方式建立了离体再生体系。结果：附加0．75mg/L BA、0．5mg/L NAA基本培养基及3w暗培养是愈伤组织诱导的最佳条件;附加0．25mg/L BA和0．1mg/L NAA的基本培养基上不定芽的诱导率最高;1／2大量元素的MS培养基附加0．1mg/l NAA、0．05mg／L和1．5％蔗糖对不定芽生根效果最好;诱导并筛选出的胚性愈伤组织在附加了0．5mg/L BA、0．5mg／L NAA的基本培养基上诱导获得大量胚状体,干化处理后大部分能经子叶胚期萌发成苗。结论：外植体的采集周期和培养条件影响胡杨离体叶片的形态发生途径。     

Expression profiles of microRNAs in oxidized low-density lipoprotein-stimulated RAW 264.7 cells

Macrophage-derived foam cells were one of the hallmarks of atherosclerosis, and microRNAs played an important role in the formation of foam cells. In order to explore the roles of miRNA in the formation of foam cells, we investigated miRNA expression profiles in foam cells through high-throughput sequencing technology. A total of 84 miRNAs were differentially expressed between RAW 264.7 macrophages and foam cells induced by ox-LDL. Thirty miRNAs were upregulated and 54 miRNAs were downregulated. GO terms and KEGG pathways analysis revealed that the target genes of most of DE miRNAs were mainly enriched in “cell differentiation,” “endocytosis,” “MAPK signaling pathway,” and “FoxO signaling pathway.” The target genes of some DE miRNAs were enriched in “Insulin signaling pathway,” “Hippo signaling pathway,” “TNF signaling pathway,” “NF-kappa B signaling pathway,” and “cell death.” Using bioinformatics analyses and dual-luciferase reporter assays, we found that miR-28a-5p and miR-30c-1-3p directly inhibited LRAD3 and LOX-1 mRNA expression through targeting the 3’UTR of LRAD3 and LOX-1 mRNA, respectively. Our study indicates that miRNAs are extensively involved in the formation of foam cells, and provides a valuable resource for further study the role of miRNAs in atherosclerosis.     

In situ detection of precursor and mature microRNAs in paraffin embedded, formalin fixed tissues and cell preparations

The in situ detection of microRNAs (miRs) expression offers several challenges. It would be advantageous to have a method which can be used in paraffin embedded, formalin fixed tissue to be able to access the large data bank of archival material. Further, it would be helpful if one could differentiate between precursor and mature, active forms of the miR. In this review, two different methods for the in situ detection of miR in paraffin embedded, formalin fixed tissues are described. Detection of the inactive precursor miR can be accomplished by RT in situ PCR. This will allow the detection of one copy of a given pre-miR per cell. Detection of the mature form of a given miR can be accomplished with in situ hybridization with a labeled probe in which some of the nucleotides have been modified; this is referred to as a locked nucleic acid (LNA) probe. An intense signal after in situ detection with the LNA probe documents marked up-regulation of the, typically, mature miR. Further, one can easily determine the specific subcellular compartmentalization of the precursor and mature forms which may provide insight into the modulation of these important regulatory molecules and their targets.     

胡杨、灰叶胡杨生物生态学特性调查

对胡杨、灰叶胡杨6个不同居群的分布、生境概况、生物学、生态学特性进行了调查,研究结果表明生境条件不同,居群的开花物候期、生长发育状况、花果产量、种子繁殖和营养繁殖以及群落的结构、繁茂程度等有所不同。地下水位在3～7m的居群,生长发育不良,种子繁殖和营养繁殖率很低,群落年龄结构老化,居群呈衰退趋势,影响因素是地下水位、土壤水分和土壤盐分的变化;地下水位在1．5～2．5m的居群,生长正常,花果产量高。胡杨、灰叶胡杨在所处各群落中均为建群种,群落垂直结构一般分为3层,群落水平结构的不郁闭性和林窗现象普遍。     

胡杨、灰叶胡杨种子营养化学成分的研究

对不同居群的胡杨、灰叶胡杨种子营养化学成分进行分析,结果表明,胡杨种子中可溶性糖、粗蛋白质、脂肪、淀粉的含量分别为9～12g·kg-1、38～44g·kg-1、21～62g·kg-1、1.9～2.3g·kg-1;灰叶胡杨种子中可溶性糖、粗蛋白质、脂肪、淀粉的含量分别为9～10g·kg-1、38～48g·kg-1、14～41g·kg-1、2.3～2.5g·kg-1.胡杨、灰叶胡杨不同居群种子中大量元素含量均以N最高,分别为6.0～6.9g·kg-1、6.3～7.6g·kg-1;微量元素含量排序一致,依次为Fe>Zn>Cu>Mn>Pb>Ni>Cd.统计分析表明,不同居群种子中可溶性糖、粗蛋白、粗脂肪、N、P、K、Ca、Mg的含量均呈现极显著差异;而淀粉与微量元素含量除一些差异不显著外,其余均达显著或极显著水平.     

盐胁迫下胡杨cDNA文库的构建及其nhx基因的克隆

采用CTAB法提取经600 mmol·L^-1 NaCl胁迫处理后的胡杨总RNA,利用SMART技术构建载体为λTriplEx2的盐胁迫条件下胡杨的表达型cDNA文库（SSL）。文库的滴度为1.2×10⁶ pfu·ml^-1,重组率约为90.6%,扩增后的滴度为3×10⁹ pfu·ml^-1,容量约为2.4×10¹¹。插入片段长度均大于400 bp,平均长度约为790 bp。从文库中随机挑选32个阳性克隆进行3′端测序,并将测序结果通过NCBI (National Center for Biotechnology Information) 数据库进行比较,发现有23个EST序列与已知序列有明显的同源性,而其余的与NCBI中的已知序列相似性较低（e值>10^-4）,可能是未知基因。其中序列SSL061、SSL179与脱水素序列有较高的序列一致性。同时合成引物,通过PCR扩增文库的方法,从中筛选获得存在于植物细胞膜上并在植物受盐胁迫时起重要作用的nhx基因,进一步验证了文库的质量。     

古墓中胡杨心材的挥发性化学成分

利用GC-MS联用技术分析了古墓中2000多年前胡杨(Populus euphratica)心材的挥发性化学成分,并应用色谱峰面积归一化法计算了各成分的相对含量。共分析确认了31种挥发性成分,主要为倍半萜类化合物和酯类化合物。